JP2005292369A - Image forming apparatus - Google Patents

Abstract

An image detection means for measuring physical properties of an image control developer image in a process of transporting the image control developer image on a recording medium after fixing, and the detection result by the image detection means Accordingly, in an image forming apparatus equipped with a mechanism for controlling the image forming conditions and adjusting the physical properties of the image, adhesion of paper dust or toner wax on the recording medium in the image detecting means, or the recording medium or person during jam processing An image forming apparatus is provided that outputs an image with stable properties such as color reproducibility and prevents damage and contamination due to hand contact.
In a post-fixing conveyance path 69, an opening W for a detection unit of an image detection unit S1 is provided at a portion of the recording medium P being conveyed facing the image control developer image forming surface. The opening / closing member S that can open and close the opening W is provided, and the image detecting means S1 enters and retracts into the post-fixing conveyance path 69 in conjunction with the opening / closing operation of the opening W by the opening / closing member S.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus of an electrophotographic system or an electrostatic recording system, such as a copying machine, a printer, etc., that develops a latent image formed on an image carrier with a developer, transfers the image to a recording medium, and fixes the image. Alternatively, the present invention relates to a configuration of an image forming apparatus used as an output device such as a multifunction peripheral or a workstation having these functions.

  Conventionally, in an electrophotographic image forming apparatus, an electrophotographic process unit, which is a plurality of image forming units in which a charging device and a developing device are arranged around a photoreceptor used as an image carrier, is juxtaposed in the apparatus, and each process is performed. After a latent image is formed on the surface of the photosensitive member by forming an optical image on the surface of the photosensitive member in the unit with an exposure device using laser, LED light, etc., and the latent image is visualized with toner by a developing device The composite developer image (toner image) on the recording medium is sequentially transferred from the photosensitive member to the intermediate transfer belt and transferred to the recording medium in a lump or directly transferred from the photosensitive member directly to the recording medium. In recent years, a tandem type image forming apparatus that fixes a toner and forms a color image has been put into practical use.

  In addition, color image forming apparatuses employing an electrophotographic system such as a color printer and a color copying machine are required to have higher output image quality.

  However, in the color image forming apparatus, the color of the obtained image fluctuates when a change in each part of the apparatus occurs due to environmental changes or long-term use. In particular, in the case of an electrophotographic color image forming apparatus, even slight environmental fluctuations may cause color fluctuations, possibly resulting in a loss of color balance.

  Therefore, means are provided for stably reproducing the color, density and gradation.

  As means for stabilizing the color and gradation, for example, in the image formation of each color, several kinds of process conditions such as exposure amount and development bias corresponding to the absolute humidity are changed, a look-up table (LUT), etc. In any of these means, the process conditions and gradation at that time are determined based on the absolute humidity measured by the temperature / humidity sensor provided in the image forming apparatus. The optimum correction value is selected.

  Further, in order to obtain a constant color, density, and gradation, even if fluctuations occur in each part of the apparatus, each color developer is used, and each density detection developer image (patch) is transferred to an intermediate transfer member or The density of an unfixed single color toner patch formed on a photoreceptor is detected by a density detection sensor for unfixed toner (hereinafter referred to as “density sensor”), and the exposure amount, development bias, etc. are detected based on the detection result. The image forming conditions and the gradation correction means such as the LUT are fed back to perform density control, thereby obtaining a stable color, density, and gradation.

  However, density control using a density sensor detects patches by forming a patch on an intermediate transfer member or drum, and controls the change in image color balance due to subsequent transfer to a recording medium and fixing. Not done. The color balance also changes depending on the transfer efficiency in transferring the toner image to the recording medium, and heating and pressurization by fixing. This change cannot be handled by density control using the density sensor as described above.

  Therefore, as disclosed in Patent Document 1, cyan (C), magenta (M), yellow (Y), and black (K) single-color gradation patches or C, M, and Y mixed colors on a recording medium. A color image forming apparatus has been devised in which image detecting means (hereinafter referred to as “color sensor”) for detecting the physical properties, usually density or chromaticity of a patch on a recording medium is formed after fixing the patch. .

  As shown in FIG. 7, the color sensor S <b> 1 as an image detection unit used here is an optical sensor having a light emitting unit 100, a light receiving unit 101, and a CPU 102. Irradiation light generated from the light emitting unit 100 is reflected by the patch image 82 of the recording medium P, and the reflected light is received by the light receiving unit 101. The amount of the received reflected light is converted into an output voltage via the CPU 102, and the output value is converted into the density and chromaticity of each part of the patch 82 by the control means of the apparatus main body.

  In this color image forming apparatus, the detected result is fed back to a calibration table for correcting the exposure amount of the image forming unit, image forming conditions (process conditions), density-gradation characteristics, and the like on the recording medium. It is possible to control the density or chromaticity of the formed final output image.

  In this method, the output image of the color image forming apparatus can be detected by an external image reading apparatus or a densitometer / colorimeter and the same control can be performed, but this method is controlled in the color image forming apparatus. Is excellent in that it completes.

  The color sensor S1 uses, for example, three or more light sources having different emission spectra such as red (R), green (G), and blue (B) as light emitting elements in the light emitting unit 100, or the light emitting elements are white (W ) Is used to form three or more types of filters having different spectral transmittances such as red (R), green (G), and blue (B) on the light receiving element. As a result, three or more different outputs such as RGB output can be obtained.

  Here, as described above, the color sensor S1 is used to control the image forming conditions based on the detection of the density and chromaticity in the image fixed on the recording medium, and to control the density or chromaticity. FIG. 8 is a sectional view showing the structure of a color LBP which is a conventional image forming apparatus, and a specific operation function will be described with reference to FIG.

  As an operation of these printers, a normal print mode in which an image forming process for obtaining a desired image is executed, and patches are formed as described above, and the color sensor S1 is used for the chromaticity, density, and gradation thereof. There is a test mode for detecting the characteristics and adjusting the image forming conditions in the normal mode.

  First, the operation in the normal print mode will be described.

  The illustrated LBP is a four-drum full-color LBP, and 50Y, 50M, 50C, and 50K are photosensitive drums, and developing devices 53Y, 53M, which contain developers (toners) of yellow, magenta, cyan, and black, respectively. 53C and 53K are provided in each of the image forming units Y, M, C, and K.

  In each of the image forming units Y, M, C, and K, the surface of each of the photosensitive drums 50Y, 50M, 50C, and 50K is scanned with a desired image document from the corresponding laser scanner device 51Y, 51M, 51C, and 51K. It is exposed by laser light emitted based on image data from an image data input unit (not shown) such as a device or a computer keyboard, and a latent image is formed. Further, by developing devices 53Y, 53M, 53C, and 53K, respectively. Development is performed with developers of yellow, magenta, cyan, and black to form a developer image (toner image). In this image forming apparatus, an intermediate transfer belt 52 that is a belt-like intermediate transfer member is provided, and a toner image for each color formed by the photosensitive drums 50Y, 50M, 50C, and 50K is primarily transferred. A sheet P as a recording medium is stacked on the paper feed cassette 53, fed by a paper feed roller 54, transported by a feed / retard roller pair 55, and transport roller pairs 56, 57, and stopped driving. It is conveyed to the roller pair 59.

  When feeding from the multi-feeding unit 40 is designated, sheets P as recording media are stacked on the multi-feeding tray 41 and fed by the multi-feeding roller 42, and a pair of conveying rollers 57. And is conveyed to the registration roller pair 59 that has stopped driving.

  After the skew is corrected by the registration roller pair 59, the sheet P is conveyed to the secondary transfer unit 60 at a predetermined timing, and the toner image on the intermediate transfer belt 52 is transferred, and then the secondary transfer device 60. The secondary transfer roller 60a and the intermediate transfer belt 52 convey the toner image to a fixing means (fixing device) 61 to fix the toner image.

  When FD paper discharge is specified for discharging the sheet P with the image forming surface down, the sheet P after fixing passes the upper side of the flapper 67 by moving the flapper 67 by control means and drive means (not shown). The paper is conveyed to the paper roller pair 62 and conveyed to the conveyance path 69. The sheet P conveyed to the conveyance path 69 is conveyed by a discharge roller pair 68 and a discharge roller 63 provided in the sheet P discharge port downstream of the sheet P conveyance direction, and forms an image on the discharge tray 64. It is discharged and loaded with the side down.

  In addition, when FU paper discharge is specified with the image forming surface facing upward, the flapper 67 is moved by control means and drive means (not shown) so that the sheet P that has passed through the fixing device 61 is placed under the flapper 67. The sheet passes through the side, is conveyed by the pair of discharge rollers 65, and is discharged and stacked on the discharge tray 66 with the image forming surface facing up.

  Next, the operation in the test mode will be described.

  The test mode is set when the test mode is designated through an operation panel (not shown) on the printer or an external input means such as a personal computer connected to the printer, or when a control unit (not shown) changes the environment, each part of the apparatus. This is executed when a test mode is automatically designated according to the result of detecting a change in the number of times.

  In the test mode, when execution of the test mode is specified as described above, a test pattern (patch) signal is generated from a signal generation circuit (not shown) provided in the control unit of the image forming apparatus, and the test pattern (patch) is generated. The surface of each of the photosensitive drums 50Y, 50M, 50C, and 50K is exposed by laser light emitted based on the signal data, and an electrostatic latent image for image control (patch latent image) is formed. Thereafter, a test pattern toner image (patch), which is a developer image for image control, is formed on the sheet P in the same development process and transfer process as in the normal print mode, and is conveyed to the fixing device 61 to be toner. The image is fixed.

  Here, the image forming conditions for forming the patch based on the patch signal are set in the memory of the control unit so as to have an appropriate density and an appropriate gradation, and the intensity of the laser beam for forming the latent image, This is a predetermined condition in which conditions such as a developing bias and a transfer bias are determined.

  An example of the patch pattern 82 formed on the sheet P is shown in FIG. The patch pattern 82 for density or chromaticity control is a gray tone patch pattern that is the center of the color reproduction area and is a very important color for achieving color balance. A gray-scale patch 80 (80a, 80b, 80c, 80e,...) Of only black (K) and a process gray-scale patch 81 in which yellow (Y), magenta (M), and cyan (C) are mixed. (81a, 81b, 81c, 81e,...), Such as 80a and 81a, 80b and 81b, 80c and 81c, etc. Only the gray gradation patch 80 of (K) and the process gray gradation patch 81 are arranged in pairs.

  The sheet P that has passed through the fixing device 61 and on which the patch pattern 82 is formed on the surface P1 passes through the upper side of the flapper 67 by moving the flapper 67 to a position indicated by a solid line by control means and driving means (not shown). The sheet P conveyed to the conveyance path 69 by the paper roller pair 62 and conveyed by the paper discharge roller pair 68 is conveyed by the paper discharge roller pair 63 provided at the discharge port, and the patch forming surface is placed on the paper discharge tray 64. It is discharged and loaded downward.

  At that time, the color sensor S1 is disposed in the conveyance path 69, and the color sensor S1 sequentially detects the patch 82 formed on the P1 side which is the surface on the sheet P from the patch 80a, and the detection result is displayed as an image. The density or chromaticity of the toner image formed on the sheet P is controlled by feeding back to the forming units 51Y, 51M, 51C, and 51K and adjusting the image forming conditions.

  Here, after fixing the patch 82 onto the sheet P by the fixing device 61, the conveyance path 69 in which the sheet P is conveyed to the discharge tray 64 that is a discharge section is referred to as “post-fixation conveyance path” in this specification. Shall be referred to.

  FIG. 10 shows in detail the vicinity of the position where the chromaticity and density measurement (patch detection) of the patch image 82 fixed on the sheet P by the color sensor S1 of the post-fixing conveyance path 69 is executed.

  The color sensor S1 is arranged on the side of the conveyance path 69 so as to face the sheet P1 surface at a portion immediately upstream in the conveyance direction of the sheet P of the feed roller 68 which is a pair of discharge rollers in FIG. The color sensor S <b> 1 that is an optical detection unit is configured to project and receive light toward the patch 82.

  As described above, by performing patch inspection on the patch 82 after fixing, it is possible to adjust the image of chromaticity and density according to the fixed image, and it is possible to maintain good image formation. .

  However, there are the following problems at the time of patch detection by the color sensor S1 of the patch in the conventional image forming apparatus as shown in FIG.

In order to project and receive light from the color sensor S1 that detects the patch array 82 for patch detection, the light projecting and receiving unit, which is the detection unit of the color sensor S1, is always opened to the conveyance path 69 side of the sheet P. In other words, the sensor S1 detection unit is caused by a heat transpiration component or the like due to fixing heat of the paper powder generated when the sheet P is conveyed on the conveyance path 69 in the normal mode or the wax contained in the toner. The surface of the light receiving / emitting element of the light emitting unit 100 or the light receiving unit 101 is contaminated, or the sheet P or a human hand comes into contact with the detection unit of the sensor S1 due to the removal processing of the sheet P when a jam occurs. As a result, the color sensor S1 is damaged or fouled, and detection output deterioration or reduction due to this is a problem.
JP 2003-150006 A

  An object of the present invention is to provide an image detection means for measuring the physical properties of an image, such as density and chromaticity, with respect to the image control developer image in the process of transporting the image control developer image on the recording medium after fixing. In the image forming apparatus provided with a mechanism for controlling the image forming conditions according to the detection result of the image detecting unit and adjusting the physical properties of the image such as the image density or chromaticity, the paper of the recording medium in the image detecting unit Provided is an image forming apparatus that prevents adhesion of powder or toner wax and the like, or damage or contamination due to contact of a recording medium or a human hand during jam processing, and outputs an image with stable properties such as color reproducibility. That is.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a means for forming an unfixed image on a recording medium, a fixing means for fixing the unfixed image on the recording medium, and an optical property of the image in the image fixed on the recording medium. An image forming apparatus having an image detecting means for measuring automatically,
An image control developer image is formed as the unfixed image under a predetermined condition. The image control developer image is fixed on the recording medium by the fixing unit, and then the recording medium is fixed to the fixing unit. In the image forming apparatus in which the image detection unit measures the physical properties of the image controlling developer image in a post-fixing conveyance path conveyed from
In the post-fixing conveyance path, an opening portion for the detection portion of the image detection means is provided at a portion of the recording medium being conveyed facing the image control developer image forming surface. And an opening / closing member capable of opening and closing the image detecting means, and the image detecting means enters and retracts into the post-fixing conveyance path in conjunction with the opening / closing operation of the opening portion by the opening / closing member. A forming apparatus is provided.

  According to an embodiment of the present invention, the opening / closing member opens the opening when the image property measurement for the image controlling developer image is performed by the image detecting means, and closes at other times.

  According to another embodiment of the present invention, the image detecting means has a function of causing the image detecting means to enter and retreat into the post-fixing conveyance path while being in contact with the opening / closing member during the opening / closing operation of the opening / closing member. Preferably, the guide member is a rotating member, and is in contact with the opening / closing member on the peripheral surface of the rotation.

  According to another embodiment of the present invention, the image detecting unit includes a pressurizing unit that urges the image detecting unit toward the recording medium when entering the post-fixing conveyance path.

  According to another embodiment of the present invention, a rocking fulcrum for moving the image detection unit into the post-fixing conveyance path and retracting the image detection unit is disposed downstream of the image detection unit in the recording medium conveyance direction. Is done.

  According to another embodiment of the present invention, the image detection means irradiates the image with light, measures the physical properties of the image based on the light intensity of the reflected light, and further detects the image measured by the image detection means. The physical property is image density or image chromaticity.

  The image forming apparatus of the present invention optically measures physical properties of an image in a unit for forming an unfixed image on a recording medium, a fixing unit for fixing an unfixed image on a recording medium, and an image fixed on the recording medium. An image detecting unit configured to form an image control developer image as an unfixed image under a predetermined condition, and the image control developer image is fixed on a recording medium by a fixing unit. Thereafter, in the image forming apparatus in which the image detecting unit measures the physical properties of the image toner for image control, the recording medium is conveyed in the post-fixing conveyance path in the post-fixing conveyance path in which the recording medium is conveyed from the fixing unit. An opening portion for the detection portion of the image detection means is provided at a portion of the recording medium facing the image control developer image forming surface, and has an opening / closing member that can open and close the opening portion. Is opened by the opening / closing member. The image detection means that measures the physical properties of the image such as density or chromaticity with a simple mechanism is protected against soiling except during detection because it moves in and out of the conveyance path after fixing in conjunction with the opening and closing operation of the image forming section. This makes it possible to prevent the recording medium from being conveyed in the conveyance path after fixing.

  Further, the image detecting means is provided with a guide member having a function of causing the image detecting means to enter and retreat into the conveyance path after fixing while being in contact with the opening / closing member during the opening / closing operation of the opening / closing member. Since the rotating member is in contact with the opening / closing member on the circumferential surface of the rotation, the image detecting means can smoothly enter and retreat into the post-fixing conveyance path in conjunction with the opening / closing operation of the opening / closing member.

  Further, when the image detection unit is caused to enter the conveyance path after fixing, the pressure detection unit biases the image detection unit toward the recording medium side. By applying the applied pressure to the recording medium, it is possible to improve transportability and measurement accuracy.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 shows the overall configuration of the image forming apparatus of this embodiment. The overall configuration of this embodiment is almost the same as that of the conventional example in which the color sensor S1 shown in FIG. 8 is mounted. However, the fixing device 61, the recording medium conveyance path after fixing (post-fixing conveyance path) 69, and the image detection means are used. Unlike the conventional example, the configuration in the vicinity of a certain color sensor S1 is provided with a window portion and a shutter member.

  Also in this embodiment, as in the conventional example, a normal print mode for executing an image forming process for obtaining a desired image, a patch is formed, and the color sensor S1 is used for its chromaticity and density and its gradation. And a test mode for adjusting image forming conditions in the normal mode. The same reference numerals as those used in FIG. 8 are assigned to those having the same functions as those of the conventional example.

  Since the operation in the normal mode is the same as that described in the conventional example, the description is omitted here.

  In the test mode, the same operation as in the conventional example is performed until the developer image (patch) for image control is fixed on the recording medium (sheet) P. The configuration of the color sensor S1 is the same as that shown in FIG.

  That is, when a test mode is designated through an operation panel (not shown) on the printer or an external input means such as a personal computer connected to the printer, or a control unit (not shown) changes in the environment or changes in each part of the device. Is executed when a test mode is automatically designated according to the result. When execution of the test mode is designated, a test pattern (patch) signal is generated from a signal generation circuit (not shown) provided in the control unit of the image forming apparatus, and laser is generated based on the test pattern (patch) signal data The surface of each of the photosensitive drums 50Y, 50M, 50C, and 50K is exposed to light to form an image control electrostatic latent image (patch latent image). Thereafter, a test pattern toner image (patch) is formed on the sheet P in the same development process and transfer process as in the normal print mode, and the test pattern toner image is conveyed to the fixing device 61 to fix the toner image. The patch formed here has the patch pattern 82 shown in FIG. 9 described in the conventional example.

  Then, the sheet P on which the patch having passed through the fixing device 61 is formed passes through the upper side of the flapper 67 by moving the flapper 67 to a position indicated by a solid line by a control unit and a driving unit (not shown), and is discharged by the paper discharge roller pair 62. After fixing, the sheet P conveyed to the conveyance path 69 and conveyed by the paper discharge roller pair 68 is conveyed by the paper discharge roller pair 63 and discharged and stacked on the paper discharge tray 64 with the patch forming surface facing down.

  Then, during conveyance in the post-fixing conveyance path 69, measurement of the chromaticity and density of the image (patch detection) as physical properties of the image is performed by the color sensor S1 of the patch 82 formed on the sheet P. In the present embodiment, the adhesion of dirt due to the wax contained in the paper dust or toner of the sheet P to the color sensor S1 and the contact of the sheet P or human hand, etc. when a jam occurs, occur in the color sensor S1. In order to prevent the color sensor S1 from being damaged or soiled by an open / close member, an opening / closing member (shutter member) S is provided at an open portion of the conveyance path 69 with respect to the color sensor S1 in the post-fixing conveyance path 69. The feature is that S is closed.

  2, 3, and 4 are enlarged views of the periphery of the post-fixing conveyance path 69 and the color sensor S <b> 1. Here, the operation of the color sensor S1 that operates in conjunction with the shutter opening / closing operation and the shutter opening / closing operation will be described.

  As shown in these drawings, in FIG. 1, the feed roller 68 that is a pair of discharge rollers is disposed on the side of the conveyance path 69 so as to face the surface of the sheet P1 at a portion immediately upstream in the conveyance direction of the sheet P. Yes. The color sensor S <b> 1 that is an optical detection unit is configured to project and receive light toward the patch 82.

  The post-fixing conveyance path 69 is provided with a window portion W that is an open portion serving as an entrance for light received by the detection portion of the color sensor S1 so as to face the patch forming surface P1 of the sheet S. The shutter member S that opens and shields the window W from the post-fixing conveyance path 69 by an actuator operation (not shown), and the pressure member SP that pressurizes and urges the color sensor S1 toward the post-fixing conveyance path 69. The roller R as a guide member is installed at the contact portion with the shutter member S (when the shutter member S is closed) at a portion that does not overlap both ends of the color sensor S1 and the sheet P in a direction intersecting the sheet P conveyance direction. The color sensor S1 is provided with a support portion C that swings and supports the shutter S itself at the downstream end in the sheet P conveyance direction.

  Here, FIG. 2 shows a state in which the color sensor S1 is retracted. The shutter member S is in a state in which the window portion W provided in a part of the post-fixing conveyance path 69 is closed. In the normal print mode, the retracted state of the color sensor S1 is maintained in this way.

  A case where the test mode is shifted from the normal state will be described below.

  In FIG. 3, the test mode is designated, and the shutter S moves in a direction parallel to the conveyance path 69 (downward in FIG. 3) as shown by the downward arrow in FIG. The state where the window portion W is opened with respect to the conveyance path 69 is shown. At this time, the sensor S1 makes the roller R contact with the shutter member S, so that the roller R rotates in the movement of the shutter member S, and the sensor S1 does not move in the same direction as the shutter member S but opens. In a state in which the window W is pressed by the pressing member SP, the support member C enters the conveyance path 69 using the swinging fulcrum.

  In this state, the sheet P having the patch pattern on the surface P1 is conveyed in the upward direction in the conveyance path 69 here.

  At this time, the sheet P is pressed by the color sensor S1 in a direction orthogonal to the conveyance direction of the sheet P by the pressing member SP, and the sheet P is rotationally guided by the roller member R, thereby realizing stable conveyance. The

  Here, even if the behavior in the conveyance path 69 of the sheet P becomes unstable by arranging the swing fulcrum C of the color sensor S1 downstream in the conveyance direction of the sheet P, the color sensor S1. As in the case where the swing fulcrum C is disposed upstream in the conveyance direction of the sheet P, the sensor S1 is pushed away, and by allowing the sheet P to enter, the behavior is not deteriorated and a jam is not induced. It becomes possible to.

  In this state, patch detection is stably performed.

  After a series of test modes are completed and the detection operation by the color sensor S1 is stopped, as shown in FIG. 4, the shutter S is moved in the opposite direction (upward in FIG. 4) when the shutter S is opened by an actuator not shown. Then, the window portion W is blocked, and the color sensor S1 is retracted from the conveyance path 69.

  At this time, the roller R serving as the guide member performs a retracting operation while being in rolling contact between the shutter S and the sensor S1, so that the test mode can be smoothly terminated without disturbing the operation of the shutter S. it can.

  That is, since the guide member for moving the shutter member S has a roller shape, the color sensor S1 can smoothly enter and retreat into the post-fixing conveyance path 69 in conjunction with the opening / closing operation of the shutter member S. It becomes.

  FIG. 5 shows a state in which the shutter S is moved and the window portion W is closed from the state where the shutter S is moved and the window W is in an open state (see FIG. 5A) as viewed from the sheet P side. (FIG. 5B) is shown. In the present embodiment, the opening / closing operation of the shutter S is executed by the parallel movement as described above.

  The operation of the shutter S is not limited to a linear one as shown in FIG. 5, but as shown in FIG. You may make it make it a closed state (FIG.6 (b)) from a)).

  As described above, a shutter is provided at the open part of the post-fixing conveyance path with respect to the color sensor, and sheet dust or toner wax adheres to the sensor by closing this shutter except during the test mode. It is possible to avoid contact of a human hand or sheet with the sensor during jam processing, and it is possible to prevent deterioration in patch detection accuracy due to sensor breakage or contamination, so that image control can be performed well and suitable image formation can be maintained. .

  The configuration of the image forming apparatus is not limited to that shown in FIG. 1 and can be applied to a single color image forming apparatus or an electrostatic recording type image forming apparatus. The dimensions, materials, shapes, relative positions, and the like are not intended to limit the scope of the present invention only to those unless otherwise specified. For example, a color image forming apparatus using a so-called photosensitive belt that directly forms an image on a belt-shaped image carrier may be used.

  The image forming apparatus shown in FIG. 1 is an intermediate transfer type image forming apparatus using a so-called intermediate transfer belt, but is a so-called belt-shaped or drum-shaped transfer conveying body that performs direct transfer while conveying on a recording medium. It may be an image forming apparatus using the above.

  Further, the mechanism for retracting the color sensor from the post-fixing conveyance path by the shutter member is not limited to the configuration using the roller and the pressure member as in this embodiment.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. FIG. 4 is a partial schematic configuration diagram illustrating a state in which the image detection unit is retracted from a post-fixing conveyance path in an example of the present invention. FIG. 4 is a partial schematic configuration diagram illustrating a state in which an image detection unit has entered a post-fixing conveyance path in an example of the present invention. FIG. 4 is a partial schematic configuration diagram illustrating a state in which the image detection unit is retracted from a post-fixing conveyance path in an example of the present invention. It is explanatory drawing which shows an example of the opening / closing operation | movement with respect to the open part of the opening / closing member which concerns on this invention. It is explanatory drawing which shows the other example of the opening / closing operation | movement with respect to the open part of the opening / closing member which concerns on this invention. It is a schematic block diagram which shows an example of an image detection means. It is a schematic block diagram which shows an example of the conventional image forming apparatus. It is a front view showing an example of a developer image for image control. FIG. 10 is a partial schematic configuration diagram illustrating states of a post-fixing conveyance path and an image detection unit in an example of a conventional image forming apparatus.

Explanation of symbols

61 Fixing device (fixing means)
69 Post-fixing conveyance path C Support member (swing fulcrum)
P sheet (recording medium)
R Roller member (guide member)
S Shutter member (opening / closing member)
S1 Color sensor (image detection means)
SP spring (pressure member)
W Window part (open part)

Claims (8)

Means for forming an unfixed image on a recording medium; fixing means for fixing the unfixed image on the recording medium; and image detecting means for optically measuring physical properties of the image fixed on the recording medium; An image forming apparatus comprising:
An image control developer image is formed as the unfixed image under a predetermined condition. The image control developer image is fixed on the recording medium by the fixing unit, and then the recording medium is fixed to the fixing unit. In the image forming apparatus in which the image detection unit measures the physical properties of the image controlling developer image in a post-fixing conveyance path conveyed from
In the post-fixing conveyance path, an opening portion for the detection portion of the image detection means is provided at a portion of the recording medium being conveyed facing the image control developer image forming surface. And an opening / closing member capable of opening and closing the image detecting means, and the image detecting means enters and retracts into the post-fixing conveyance path in conjunction with the opening / closing operation of the opening portion by the opening / closing member. Forming equipment.   2. The image forming apparatus according to claim 1, wherein the opening / closing member opens the opening when the image detecting unit measures the image physical properties of the image controlling developer image, and closes at other times.   The image detection means is provided with a guide member having a function of causing the image detection means to enter and retreat into the post-fixing conveyance path while being in contact with the opening / closing member during the opening / closing operation of the opening / closing member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the guide member is a rotating member and is in contact with the opening / closing member on a circumferential surface of the rotation.   5. The image formation according to claim 1, further comprising a pressing unit that biases the image detection unit toward the recording medium when the image detection unit enters the post-fixing conveyance path. apparatus.   2. The rocking fulcrum for moving the image detection means into and after the fixing conveyance path into the post-fixing conveyance path is provided on the downstream side in the recording medium conveyance direction with respect to the image detection means. The image forming apparatus according to any one of items 5 to 5.   The image forming apparatus according to claim 1, wherein the image detection unit irradiates the image with light and measures physical properties of the image based on a light intensity of the reflected light.   The image forming apparatus according to claim 1, wherein the physical property of the image measured by the image detection unit is an image density or an image chromaticity.

Images